If I use the web interface (Settings->General->Upload File(s) ) to upload the DuetWebControl-1.19.zip, DuetWiFiFirmware-1.19.bin and DuetWiFiServer-1.19.bin files they will go automatically in their folders as it should? ( DuetWebControl-1.19.zip to /www and DuetWiFiFirmware-1.19.bin DuetWiFiServer-1.19.bin to /sys ?)

Yes they should go to the correct places, although you will have to rename DuetWebControl-1.19.zip to e.g. DWC.zip otherwise your existing version of the web interface will refuse to upload it. The complication is that you may have old web files in /www depending on when your Duet was supplied, and it's best to remove them if so.